• 대한기계학회논문집A
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• 제29권7호
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• pp.1028-1034
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• 2005

In this paper, the failure analysis of an optical disk drive is carried out and the limit ranges of the misalignment f3r the higher performance are presented. Since optical disks are removable from optical disk drive, the translational and angular misalignments, which causes read/write errors, always exist. Therefore, the limit ranges of the misalignment should be investigated. For this reason, the failure analysis by the vibration analysis is studied. The influences of the misalignment are tested by the aging test. And the limit ranges of the misalignment are proposed for the reliability of optical disk drives.

• 한국IT서비스학회지
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• 제7권2호
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• pp.181-195
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• 2008

The rapid growth of mobile communication technology has provided the expansion of mobile internet services, particularly mobile realtime transaction takes much weight among mobile fields. There is an increasing demand for various mobile applications to process transactions in a mobile computing fields. Thus, During transmission in wireless networks a base station failure inevitably causes data loss of the base station buffer. It is required to compensate the loss for communication. The existing methods for a base station failure are not adequate because they all suffer from too much overhead and resolve only the link failure. In this paper, we study an efficient recovry systems for a mobile DBMS. We propose SLL (Segment Log List) that enables the mobile host to compensate data loss efficiently in the case of base station failure. In SLL, a base station deliveries an output information of data cells to a mobile host. when a base station fails, the mobile host can retransmit just next data cells. We also prove the efficiency of new method.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권4호
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• pp.331-341
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• 2009

PSA (Pressure Sensitive Adhesive) is used for various purposes in electronic appliances such as double-sided tape for fitting parts, product's name plate, and surface protecting film, and so forth. In several kinds of PSAs, this paper dealt with the failure analysis of PET (Polyethylene Terephthalate) acrylic adhesive tapes. The causes of interface failure were investigated through the test of adhesive strength, thickness, and structure. And test standard methods to prevent recurrences were established.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 추계학술발표 개요집
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• pp.19-34
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• 1996

A review was made of fatigue failures of nuclear power plant components in Japan, which were experienced in service and during periodical inspection. No case has been recently reported of a service fatigue failure of a reactor pressure vessel itself, excluding nozzle corner cracks, that occurred many years ago. But, service fatigue failures have been occasionally experienced in piping systems, pumps, and valves, on which fatigue design seems to have been inadequately applied. The causes of fatigue failures can be divided into two categories: mechanical-vibration-induced fatigue and thermal-fluctuation-induced fatigue. Vibration-induced fatigue failure occurs more frequently than is generally thought. The lesson gleaned from the present survey is a recognition that a service fatigue failure may occur due to any one or a combination of the following factors: (1) lack of communication between designers and fabrication engineers, (2) lack of knowledge about a possibility of fatigue failure and poor consideration about the effects of residual stresses, (3) lack of consideration on possible vibration in the design and fabrication stages, and (4) lack of fusion or poor penetration in a welded joint.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(III)
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• pp.36-41
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• 2003

Among welded structure bogies in use for high speed freight car, a part of bogies manufactured in 1999 and 2000 have found problems that failure occurs in its end beam. In case of a freight car a difference of weight between empty and loading conditions are worse than in case of a passenger car. Moreover its brake system is tread brake without second suspension system. A failure of end beam is supposed to be due to loading by brake rather than vertical loading by freight. This failure can make brake system useless and may be a cause of derailment in the worst case. In this study, we have proposed a simple torsion-free brake shoe holder hanger to remove torsion of hanger bracket which is supposed to be one of causes of failure and performed finite element analyses for making trial manufactures and its application.

• 한국군사과학기술학회지
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• 제13권5호
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• pp.769-774
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• 2010

It happened fractures on special bolt which supported main landing gear actuator up-lock rod of aircraft. Cracks were initiated mainly from the center hole and the external thread of the special bolt. To find out failure root causes, metallographic, fractographic analyses as well as test work were carried out. From the fractographic study by SEM work, fracture occurred by a brittle intergranular type failure. The fracture could be occurred primarily by solid-metal-induced embrittlement due to cadmium embrittler penetrated into the flaw existed after machining work for center hole and thread on the bolt during baking treatment processing to eliminate hydrogen. For its successful application, cadmium EP bolts require proper and adequate baking treatment after electroplating, and make no more drilled center hole on the bolt to prevent same failure.

• Nuclear Engineering and Technology
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• 제40권1호
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• pp.1-8
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• 2008

One of the major current challenges to nuclear energy lies in its competitiveness. To stay competitive the industry needs to reduce maintenance and fuel cycle costs, while enhancing safety features. Extended burnup is one of the methods applied to meet these objectives However, there are a number of potential fuel failure causes related to increased burnup, as follows: l) Corrosion of zirconium alloy cladding and the water chemistry parameters that enhance corrosion; 2) Dimensional changes of zirconium alloy components, 3) Stresses that challenge zirconium alloy ductility and the effect of hydrogen (H) pickup and redistribution as it affects ductility, 4) Fuel rod internal pressure, 5) Pellet-cladding interactions (PCI) and 6) pellet-cladding mechanical interactions (PCMI). This paper discusses current and potential failure mechanisms of these failure mechanisms.

• Corrosion Science and Technology
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• 제20권5호
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• pp.242-248
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• 2021

Unforeseen failures of boilers in power plants may affect the continuation of electricity generation. Main failures in boilers are influenced by the tube material, tube position, boiler service temperature and pressure, and chemical composition of the feed water and coal. This investigation was intended to find answers on the causes and mechanism of failure of the fire-side boiler water-wall tubes, due to perforation and corrosion. The tube conformed to the material requirements in terms of its chemical composition and hardness. Microscopic examination showed ferrite and pearlite indicating no changes in its microstructure due to the temperature variation. SEM test showed a single layer and homogenous film density particularly on the area far from perforation. However, layers of corrosion product were formed on the nearby perforation area. EDX showed that there were Na, Ca, S, and O elements on the failed surface. XRD indicated the presence of Fe₂O₃ oxide. The failure mechanism was identified as a result of significant localized wall thinning of the boiler water wall-tube due to oxidation.

• Tuberculosis and Respiratory Diseases
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• 제50권4호
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• pp.473-483
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• 2001

연구배경 : 항결핵제에 의한 치료실패의 원인으로 약제내성균, 환자의 규칙적인 약제 복용, 감염 결핵균 종의 차이, 환자의 면역상태 등이 복합적으로 작용한다. 이에 저자들은 흉부 및 경부결핵환자들은 대상으로 항결핵제에 의한 다각적인 치료실패 원인을 분석하고자 본 연구를 시행하였다. 방 법 : 폐결핵환자 204명과 경부결핵환자 53명을 대상으로, 객담, 경부임파선 및 혈액을 채취하여 결핵균을 배양하고 변역상태를 측정하였다. 인형결핵균과 비인형결핵균의 감별, RFLP 양상 분석 및 항결핵제 감수성검사 등을 시행하였고, IL-$1{\beta}$, IL-12, $IFN{\gamma}$ 및 $TNF{\alpha}$ 등의 혈중 농도를 측정하였다. 항결핵제 치료 후 18개월까지 정기적인 경과관찰을 시행하여 완치 유무를 결정하였다. 결 과 : 결핵균의 RFLP에 따른 결핵의 난치성 여부는 관찰할 수 없었다. 총 204례의 환자들 중 31.9%(65 례)가 난치성으로 판정되었으며 난치군은 평균연령이 비교적 높고, 남자 및 재발 예가 많았다. 65례의 난치원인을 모두 추정할 수 있었으며, 혈중 IL-12 농도저하(59.4%), 다제내성균 (54.7% ), 불규칙한 항결핵제복용(15.4%), 비인형 결핵균(6.2%) 및 중감염 (4.6%) 등의 원인을 관찰할 수 있었다. 완치군과 난치군의 혈중 IL-12의 평균 농도는 $227.6{\pm}78.2$ 및 $148.9{\pm}79.7\;pg/mL$로서 난치군이 유의(p<0.01)하게 낮았다. IL-12는 165.0 pg/mL에서 최대민감도 64.7% 및 최대특이도 75.4%를 나타내였다. 53명의 임파성 결핵환자들은 대부분 완치되어 난치원인을 분석할 수 없었다. 결 론 : 결핵의 난치원인 분석에서 혈중 IL-12 농도 저하 및 약제 내성균에 의한 감염이 가장 주요한 원인으로 간주되었고, 그 외 불규칙한 약복용, 비인형 결핵균에 의한 감염 및 중감염 등의 순으로 나타났다. 한편 국내에서는 균주군에 의한 감염이 빈번하였으나 균주군 및 비균주군에 의한 약제 내성율 차이는 관찰할 수 없었다.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.82-86
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• 2015

Construction delay is a common problem worldwide, which is considered as one of the main reasons for project failure. Bangladesh construction industry is no exception. This study investigated the main causes of delay in large building construction projects in Bangladesh. A questionnaire survey was conducted to determine the causes of delay from owners, consultants, and contractors of large building construction projects. About 70 respondents participated in the survey. Using the importance index analysis, the study identified 10 most important causes of delay from a list of 30 different causes. Ten most important causes were: (1) lack of experienced construction manager, (2) lowest bidder selection, (3) funding shortage by owner, (4) lack of proper management, (5) improper planning and scheduling, (6) lack of skilled workers, (7) site constraints, (8) contractors' cash flow problems during construction, (9) escalation of resources price, and (10) contractors' excessive workload. Furthermore, Kruskal-Wallis test indicates that there is no significant variation exists among the three group of respondents, ie owners, consultants and contractors.